1. Field of the Invention
The present invention generally relates to a series-connected fan unit and, more particularly, to a series-connected fan unit that has at least one circuit board coupled with at least one positioning member, respectively.
2. Description of the Related Art
Referring to FIG. 1, a conventional series-connected fan unit 9 is disclosed by Taiwanese Patent No. I322655 entitled “Circuit Board Holder, Dual Motor Apparatus, and Dual Fan Structure”. The conventional series-connected fan unit 9 includes two cooling fans 91 and a circuit board holder 92. Both the cooling fans 91 have a motor 911, a circuit board 912 and a plurality of vanes 913. The circuit board 912 can start operation of the motor 911 which, in turn, drives the vanes 913 to rotate. The circuit board holder 92 is disposed between the two cooling fans 91 and consists of a base plate 921 and a plurality of supporters 922. The base plate 921 has two faces 923 opposite to each other. The supporters 922 are located on the base plate 921 and protrude from the two faces 923 of the base plate 921. In this arrangement, the supporters 922 can abut the two circuit boards 912 to prevent shaking of the circuit boards 912 resulting from vibration generated during operation of the two cooling fans 91.
In general, a distance D is present between the two circuit boards 912 when the two cooling fans 91 are connected in series. The circuit board holder 92 has a predetermined height H, which should be designed in a value substantially equal to the distance D in order for the supporters 922 to securely abut against the two circuit boards 912, respectively. If the two cooling fans 91 are connected too closely or the predetermined height H is accidentally designed to have a value larger than it is intended to be, the circuit board holder 92 will over abut against the two circuit boards 912 as the distance D is smaller than the predetermined height H. This not only causes damage of the two circuit boards 912 but also affects the coupling and positioning of internal components inside the conventional series-connected fan unit 9. On the contrary, if the two cooling fans 91 are not connected closely enough or the predetermined height H is accidentally designed to have a value smaller than it is intended to be, the circuit board holder 92 won't be able to reach and abut against the two circuit boards 912 as the distance D is larger than the predetermined height H. As a result, shaking and loosening of the two circuit boards 912 occur easily.
In light of the aforementioned problems, the conventional series-connected fan unit 9 generally has some drawbacks such as difficulty in securely positioning the circuit boards and a tendency in damaging the circuit boards during the assembly process. Thus, it is desired to improve the conventional series-connected fan unit 9.